Single and Two Phase Pressure Drop in Fluid

Pressure drop is of paramount importance in a fluid flow. Single phase pressure drop occurs in a pure liquid or pure gas flow. Two phase pressure drop occurs in phase changing equipments like evaporators and condensers of refrigeration air conditioning pla and heat pumps. Maximum two/ three types of pressure drop (frictional, gravitational and acceleration) can occur in a single or two phase flow. In each case, pressure drop take place in straight pipes. Several empirical equations and correlations have been developed and compared for the pressure drop. Consequently well planned pipe layout and judicious selection of proper pipe material, pipe fittings and valves will result in reducing the overall pressure drop which in turn will reduce the running cost.


INTRODUCTION
It is difference of pressure between two points in a fluid flow. These two points can be at a horizontal level or at different levels. Flow can be only liquid flow or only gas flow or mixed flow (two phase flow). The temperature difference is the driving force for heat transfer. Voltage difference is the driving force for current flow. Concentration difference is the driving force for mass transfer. Similarly pressure difference is the driving force for the flow of a f Pressure drop is extremely important in fluid flow. It should be small otherwise it increases the cost of operation of the fluid flow. Pressure drop is present in a straight pipe and also across various types of pipe fittings and valves. Only after careful analysis, @ IJTSRD | Available Online @ www.ijtsrd.com | Volume -2 | Issue -4 | May-Jun 2018 Pressure drop is of paramount importance in a fluid flow. Single phase pressure drop occurs in a pure liquid or pure gas flow. Two phase pressure drop occurs in phase changing equipments like evaporators and condensers of refrigeration air conditioning plants and heat pumps. Maximum two/ three types of pressure drop (frictional, gravitational and acceleration) can occur in a single or two phase flow. In each case, pressure drop take place in straight pipes. Several empirical equations and correlations been developed and compared for the pressure drop. Consequently well planned pipe layout and judicious selection of proper pipe material, pipe fittings and valves will result in reducing the overall pressure drop which in turn will reduce the running Pressure drop, Single phase, Two phase, It is difference of pressure between two points in a fluid flow. These two points can be at a horizontal level or at different levels. Flow can be only liquid flow or only gas flow or mixed flow (two phase flow).
temperature difference is the driving force for heat transfer. Voltage difference is the driving force for current flow. Concentration difference is the driving force for mass transfer. Similarly pressure difference is the driving force for the flow of a fluid. Pressure drop is extremely important in fluid flow. It should be small otherwise it increases the cost of operation of the fluid flow. Pressure drop is present in a straight pipe and also across various types of pipe areful analysis, judicious selection is made regarding pipe material, pipe roughness, pipe layout and orientation, fittings and valves. In this review, pressure drop analysis has been limited to a single phase flow as well as in a two phase flow

II TYPES OF PRESSURE DROP
There are three types of pressure drop. 'f' exist on both sides of the equation and can be found only by an iterative procedure. Here 'k' is the roughness of the pipe.

IV SINGLE PHASE GAS FLOW FRICTIONAL PRESSURE DROP
In compressible fluids (gases and vapors), there is a significant increase in velocity due to pressure decreases (Expansion) and hence requires a different equation as compared to that for liquids. (ii) For ( µ L / µ G ) > l000 and mass flux > l00 kg/m 2 s, the Chisholm correlation [3] is better than other correlations in agreement with the experimental data (iii) For ( µ L / µ G ) > l000 and mass flux < l00 kg/m 2 s, the Lockhart-Martinelli correlation [l] is better than other correlations in agreement with the experimental data (iv) For ( µ L / µ G ) < l000, the Friedel correlation(4) is better than other correlations in agreement with the experimental data for most of the fluids (b) Tribbe  6pf /6pf, C-S = l.46 (l-C) -l.006 (2) Where C is the concentration by mass of R-l3 The drawbacks of these correlations are that these do not allow extrapolation of pressure drops to high concentrations of R-l3, say above 25 per cent.
The mean and standard deviations for the developed correlations were found to be as given below:

CONCLUSION
Single phase and two phase pressure drop is a critical parameter in the design of a pipe flow as well as in the selection of a pipe fitting and a valve. Therefore accurate prediction of pressure drop is of utmost importance. Single phase pressure drop is estimated using Darcy equation. Two phase pressure drop is estimated by using widely accepted empirical equations. Two phase pressure drop is extremely importance in the design of phase changing equipment mainly evaporators and condensers used in refrigeration, air conditioning and heating pumps. Thus design engineer must know the pressure drop to a high degree of accuracy to ensure proper pipe design and selection of a pipe fitting and a valve. Pressure drop and flow rate are dependent on one another. The higher is the flow rate, the greater will be the pressure drop and vice versa. In every application, pressure drop must be kept to a minimum possible level in order to reduce the running cost of pipe flow. It can be achieved by the judicious selection of the pipe material, pipe roughness, pipe layout, pipe orientation, pipe fittings and valves